﻿<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>03 侧边栏效果</title>
    <style type="text/css">
        * {
            padding: 0;
            margin: 0;
        }
        
        #box {
            width: 200px;
            height: 200px;
            background-color: red;
            position: relative;
            left: -200px;
        }
        
        #box span {
            position: absolute;
            width: 40px;
            height: 60px;
            color: #fff;
            background-color: #000000;
            right: -40px;
            top: 50%;
            margin-top: -30px;
            line-height: 60px;
            text-align: center;
        }
    </style>
</head>

<body>
    <div id="box">
        <span>拉开</span>
    </div>
    <script type="text/javascript">
        //  -200   0
        window.onload = function() {
            var box = document.getElementById('box');
            box.onmouseover = function() {
                this.style.left = 0 + 'px';
            }
            box.onmouseout = function() {
                this.style.left = -200 + 'px';
            }
        }
    </script>
</body>

</html>